The invention relates to a television camera comprising a pick-up tube which is provided with a cathode for emitting, while being heated, an electron beam, with a control electrode for the electron beam and a target plate which is scanned line-by-line and field-by-field with periodical scanning and blanking periods by the electron beam under the control of deflection means.
Such television cameras comprising pick-up tubes are generally known. Depending on whether the camera is intended for use in black-white or color television, one or more pick-up tubes can be used, which are offered by pick-up tube manufactures in data handbooks. Thus, a choice for the pick-up tube or tubes can be made from the Philips "Data Handbook, Electron Tubes" under the heading "Camera tubes". From the present data it appears that the offered pick-up tubes are provided with an indirectly heated cathode in the electon gun, a heating filament, which is free from the cathode, being connectable to an a.c. voltage source or a d.c. voltage source of, typically, 6.3 V and, depending on the tube type, with two typical heater current values of 300 mA and 95 mA. Herefrom it follows that in the case of connection to a d.c. voltage source, the filament consumes, for the indirect heating of the cathode, a heater voltage power equal to 1.9 W and 0.6 W, respectively.